The present disclosure relates to an optical member and its production method, and particularly to an optical member including an antireflection coating on its surface, and further including a light shield part in a part surrounding the antireflection coating and a production method of the optical member.
Conventionally, an antireflection structural member (antireflection coating) is provided on a light incident surface of a lens (transparent substrate) made of transparent material, such as glass and plastic, to reduce a loss of transmission light caused by reflection at the surface.
As an antireflection structural member for visible light, a dielectric multi-layer coating, a fine uneven pattern structural member with a pitch shorter than the wavelength of visible light and the like are known (Japanese Unexamined Patent Publication No. 2005-275372 (Patent Document 1), Japanese Unexamined Patent Publication No. 2012-073590 (Patent Document 2) and the like).
Patent Document 1 discloses an optical member including, as an antireflection structural member, a fine uneven pattern coating that contains alumina as a main component. As a method for forming a fine uneven pattern coating containing aluminum oxide as a main component, a method is known in which a coating of aluminum oxide is formed by a vacuum deposition method or a liquid phase method (sol-gel method), and after then, a plate-shaped crystal coating (fine uneven pattern coating) is obtained by causing a surface layer to become boehmite by hydrothermal treatment, such as vapor treatment or hot water immersion treatment.
Meanwhile, when an optical system is constructed by using optical members, such as a lens, a light shield coating is generally provided in a ray non-effective part of the optical member to suppress generation of unwanted light that causes flare, ghost and the like.
Patent Document 2 discloses an optical member in which at least one layer of protective coating is formed on a substrate, and a light shield coating is formed on the protective coating formed in a ray non-effective part of the optical member, and also a plate-shaped crystal coating that has an uneven pattern structure and contains aluminum oxide as a main component is formed on the protective coating formed in a ray effective part.